' sWsName  - имя листа

Sub SomeSub(ByVal sWsName As String)
    Dim ws As Worksheet
On Error GoTo ErrH
    For Each ws In Workbooks("ИмяРабочейКниги").Worksheets
        If ws.Name = sWsName Then
            Exit For
        End If
    Next ws
    If ws Is Nothing Then
        MsgBox "Рабочий лист """ & sWsName & """ в данной книге не найден!", vbExclamation, ""
    End If
Exit Sub
ErrH:
    MsgBox Err.Description, vbCritical, Err.Source
End Sub